It's not repairable in the sense that it doesn't use standard parts so whether you can get replacements or not depends on where you are, geographically. If it used a standard atx psu for example, you'd be able to buy that anywhere. Same thing for the cpu, if it used a standard cpu+gpu instead of a custom apu, you'd be able to replace just that if it broke, instead of the whole motherboard. Or even upgrade it if you wanted to.

Even motherboards themselves have different features. You might need 2.5g ethernet whereas someone else is fine with gigabit but wants better wifi. In my case, I always buy boards with spdi/f to use them with a dac. You lose that flexibility with a device like this.

Regarding the OS in prebuilts, it's very common to have the option to order them without Windows. If you don't know how to install Bazzite, just pay a technician to do it. It will still be cheaper than Windows. That's not an excuse or impediment.